1. Technical Field
The present invention relates to a plasma display panel (PDP) and, more particularly, to a PDP in which front discharge electrodes and rear discharge electrodes are optimally positioned.
2. Related Art
A plasma display panel (PDP) comprises a front panel and a rear panel. The front panel comprises a front substrate, pairs of sustain electrodes composed of Y electrodes and X electrodes disposed on the rear surface of the front substrate, a front dielectric layer covering the sustain electrodes, and a protective layer covering the front dielectric layer.
Each of the Y electrodes is composed of a transparent electrode and a bus electrode, and each of the X electrodes is composed of a transparent electrode and a bus electrode. The transparent electrodes are made of indium tin oxide (ITO) or the like. The bus electrodes and are made of highly conductive metal.
The rear panel comprises a rear substrate, address electrodes disposed on the front surface of the rear substrate and intersecting the pairs of sustain electrodes, a rear dielectric layer covering the address electrodes, barrier ribs on the rear dielectric layer dividing a discharge space into discharge cells, and fluorescent layers on the sidewalls of the barrier ribs and the rear dielectric layer.
In the PDP, in addition to the pairs of sustain electrodes which generate discharge, the front dielectric layer and the protective layer are formed on the rear surface of the front substrate through which visible light generated by the fluorescent layers in the discharge cells is transmitted. Thus, transmittance of visible light is remarkably reduced and the brightness of the PDP is reduced.
Furthermore, since the pairs of sustain electrodes are formed on the rear surface of the front substrate in the PDP, the majority of the sustain electrodes must be formed of ITO, which is very expensive and highly resistive, in order to allow the generated visible light to be transmitted through the front substrate.
Thus, the production cost of the PDP is increased. Furthermore, since the high resistance of the ITO electrodes causes a voltage drop, images cannot be uniformly displayed when the PDP is large.
In the PDP, the pairs of sustain electrodes are formed on the rear surface of the front substrate, and the discharge occurs behind the protective layer and diffuses within the discharge cells. In other words, the discharge occurs on only one of the surfaces of each of the discharge cells. Thus, luminous efficiency is reduced.
When the PDP is used for a long period of time, charged discharge gas induces ion sputtering of the fluorescent material in the fluorescent layers due to an electric field, resulting in permanent after-images.
In a unit discharge cell, a pair of sustain electrodes is covered with a front dielectric layer, and the front dielectric layer is covered with a protective layer. When a pulse potential is applied to the sustain electrodes, particles in the front dielectric layer are charged, thereby generating wall charge on the rear surface of the protective layer.
At this point, the pulse potential applied to the sustain electrodes generates an electric field component, perpendicular to the rear surface of the protective layer, from the flat surfaces of the sustain electrodes, and generates an electric field component, at an acute angle to the rear surface of the protective layer, from the edges of the sustain electrodes. Thus, charge is induced over a distance wider than the width of each of the sustain electrodes on the rear surface of the protective layer.
In this case, the electric field radiating from the edges of the sustain electrodes interferes with the barrier ribs, and thus the amount of wall charge on the rear surface of the protective layer is reduced. As a result, the level of discharge at a given drive voltage is reduced, and thus power efficiency of the PDP is reduced.